1. Field of the Invention
The present invention relates to a camera module including an imaging function section, and a cable section and a connector section that couple the imaging function section to an external circuit.
2. Description of the Related Art
At present, most portable devices, such as mobile phones and PDAs, have a photographing function. A camera module that realizes such a photographing function typically has a structure described in Japanese Unexamined Patent Application Publication No. 2001-128072.
A camera module described in Japanese Unexamined Patent Application Publication No. 2001-128072 is structured such that an imaging function section including a lens unit and an image sensor IC is provided on a substrate that couples the imaging function section to an external circuit. Specifically, the substrate has an aperture. The lens unit is disposed on one principal surface side of the aperture, and the image sensor IC is provided on the other principal surface side of the aperture. A light shielding film is provided on the other principal surface of the substrate, on which the image sensor IC is mounted, to cover the image sensor IC.
However, the imaging function section of the camera module in Japanese Unexamined Patent Application Publication No. 2001-128072 has high strength because it has a structure in which multiple electronic components are mounted on both surfaces thereof. On the other hand, the imaging function section is coupled to the external circuit by the substrate, and a part having a function of coupling to the external circuit (an external wiring part) is formed only by the substrate. Hence, the strength of this part is lower than that of the imaging function section.
Therefore, when bending stress is imposed on the substrate, great stress is applied to a boundary position between the external wiring part and the imaging function section in the substrate. For this reason, the substrate may break from the boundary position. If such breakage occurs, outside light enters the imaging function section via a broken surface, and unnecessary light that does not pass through the lens unit is received by the image sensor IC.
Further, when a flexible substrate, such as a resin multilayer board, is adopted as the above-described external wiring part, the imaging function section and the external wiring part are combined by the flexible substrate while thickening the imaging function section and thinning the external wiring part.
In this case, if the external wiring part is curved by external force applied thereto, stress concentrates at the boundary between the imaging function section and the external wiring part, that is, at the boundary between portions having different thicknesses, and breakage is more apt to occur. If breakage occurs, outside light enters the imaging function section via a broken surface, and unnecessary light is received by the image sensor IC.
When a flexible substrate is used, a flexible substrate in which an imaging function section and an external wiring part are combined is formed by bonding a plurality of flexible material sheets (resin sheets) by heat and pressure. However, since the imaging function section and the external wiring part are different in thickness, bonding is sometimes not sufficient at the boundary position. Hence, the degree of adhesion between the material sheets, that is, between dielectric layers may decrease. If the degree of adhesion between the dielectric layers is low in this way, unnecessary light may pass through interfaces between the dielectric layers, and the unnecessary light may be received by the image sensor IC.